It’s not clear what role Levi will play in the Sony Pictures adaptation, as he’s at least a couple of years older than the protagonist, Harold. Levi has played a kid in an adult body before, however (see:
Shazam!), so maybe it’s not out of the realm of possibility. And Harold would seem to be the only starring character from the original source material, though Johnson wrote five other books in the series as well. Or, in the realm of complete speculation, perhaps Levi is taking on the role of the purple crayon itself, transforming Harold’s magical drawing instrument into some live-action version of Microsoft’s discontinued Clippy.